So Google crafted new changes in their algorithms specifically, and intentionally, to bring about negative SEO en masse. Predictably, the industry responds with, "Please, please give us a disavow links tool". When the negative SEO hysteria hits an all-time high, Google finally responds and gives us a tool that will turn SEO's and SEM's all over the world into free outsourced labour to manually do Google's job for it. The disavow links tool is completely anti-SEO as you might expect. It is like handing people shovels to dig 6 foot holes in the dirt with the promise of gold, and then burying them in it. It's a user-powered tattle-tale machine and it will serve no good for anyone but Google.
It’s a classic example of the Hegelian Dialectic in use, this time not by a government, but by Google. Don't be fooled.
Matthew Woodward has written a detailed article about it that is well worth reading at Why Google Disavow Is Bad News For SEO - Matthew Woodward
Source: Matt Cutts and Google’s Disavow Links Tool is a Trojan Horse for SEO & SEM | Articles for Website Developers | Web Design Front